Sheet separating mechanism



. July 19, 194.9,

'- l H. T. BACKHOUSE SHEET SEPARAT'ING MECHANISM Filed May 26, 1948INVENTOR.

Patented July 19, 1949 it-F E SHEET MECHANISM Headl'ey TownsendBackhouse, Wentworth,

' England Application May 26, 1948, Serial No. 29,210 In Great BritainDecember 11, 1946 This invention relates to sheet separating mechanismfor use in separating and feedin sheets of paper, card or the like, oneat a time, from the top of a pile or stack for feeding to a printing orother machine and of the typ comprising in combination a suction ormechanical gripper (usually a suction gripper) arranged to grip eachuppermost sheet in the pile in turn at or near the rear edge of thesheet considered in relation to the direction of feed and to lift theedge, and a presser foot, or second sheet stop. which engages underpressure the remainder of the pile to prevent movement of asecond sheetduring the removal of the separated sheet.

Apparatus of the kind described is usually used in combination withsheet forwarding devices for feeding the separated sheets to a printingpress or other machine operating on sheets, the sheets being fed singlyor in a continuous'stream of partly underlapped or overlapped sheets.The separating and lifting grippers aforesaid may be given a forwardingmovement (1. e. in a direction substantially parallel to the plane ofthe top of the pile) to initiatethe feeding of each sheet or theseparating grippers may transfer the sheet to forwarding grippers (e. g.suckers) which are given a forwarding movement.

The present invention is concerned with improvements in the presser footor second sheet stop employed in a sheet separator of the type describedand with a method of separation in which such a presser foot isemployed.

The invention provides a sheet separator of the type described,characterized by means for increasing, continuously or by one or moresteps, the pressure applied by the presser foot to the upper surface ofthe pile during the separation of each sheet.

It is an advantage of sheet separators having the characteristic featureof the invention that the initial pressure applied, by the presser footmay permit the sheet being separated tobe withdrawn from underneath thepresser foot and the increased pressure exerted by the presser foot maythenbe employed to clamp the remaining sheets and prevent movementthereof. The method of separating sheets which .includes the step ofwithdrawing the sheets'one at a time from beneath a retaining member atthe rear of the pile accordingly constitutes an important feature of theinvention.

It is customary to employ a spring for urging the presser foot intopressure engagement with the pile and according to the present inventionin 15 Claims. 271-26) one of its forms, means are provided for increas-2 ing. the force exerted by such a spring after the presser foot hasengaged the pile. These means may, for example, include areactionabutment for the spring which is movable to increase the loading of thespring. after engagement of the presser foot with the pile. c A cam maybe. employed for controlling the action of the spring in lowering thepresser foot into engagement with the pile, and the same cam may bearranged to move, through appropriate linkwork, the reaction abutment asaforesaid after the presser foot has been lowered.

In an alternative arrangement, one spring is employed for lowering,under cam control, the presser foot on to the pile and for applying theinitial pressure to the pile and a second spring under variable loadingis employed for increasing the pressure. A cam controlled movable anchoror abutment may be employed for increasing the loading of the secondspring and the cam used for this purpose may be independent of thatemployed for lifting and lowering the presser foot. I

The invention also provides the method of separating sheets one at atime from the top of a pile or stack for feeding to a printing. or othermachine which comprises the steps of applying limited downward pressureto the uppermost sheet of the pile at or near the rear edge thereof bypresser means engaging the pile, engaging and gripping the sheet at ornear the rear edge by gripper means, lifting the edge by the gripper.means to withdraw the edge from under the presser means, applyingincreased downward pressure to the pile (e. g. by increasing thepressure exerted by the aforesaid presser means) and directing a blastof air between th uppermost sheet and the remainder of the pile.

In the preferred form of the method just described the air blast isdirected through the presser means.

It is also preferred in carrying out the method to direct one or moreblasts of air into the'top portion of the pile at the back beforeengage-' ment of the pile by the pressermeans in order to effect aninitial, partial separation of the sheets.

Two specific forms of apparatus for carrying out the invention will nowbe described-by way of example and with reference to the accompanyingdrawings, in which Figs. 1 and 2 are diagrammatic side views of saidforms.

In each of these two. examples, the apparatus operates at the'rear ofthe pile and there are two or more suction grippers i operating abovethe 3 pile 2 near to the rear edge. Each gripper, which is given risingand falling movements, is lowered on to the pile to engage eachuppermost sheet 3 in turn and is then lifted while gripping the sheet.The lifted rear edge of the sheet is then transferred to forwardingsuction grippers (not shown). In each example, there is associated witheach separating gripper ,a presser foot 4 consisting of a foot carriedon a bell crank lever I rotatablymounted on a shaft 6 extending parallel to the rear edge of the pile behind and slightly above the top ofthe pile. Both exainples are arranged for feeding the separated sheetsin a stream which may be arranged to be of partly underlapped oroverlapped formation.

In both examples also air blast means, comprising one or more blastnozzles 25, is so disposed as to fluif the sheets near the top of thepile,

and surrounded by a compressionspring l3, tending to maintain thefollower in contact with the I cam and to lower the foot on to the pile.

In the operation of the arrangement as so far described the cam 8controls the lowering of the foot on to the top of the pile under theaction of the spring in such timed relationship with the movement of theseparating gripper that the foot lightlyengages the uppermost sheetbefore and as it is lifted by the gripper I. The engagement is such thatthe gripper may withdraw the sheet from under the foot. The pressureexerted by the foot on the pile is then increased by the means about tobe described and, at the same nected to a rod ll slidable in a guidebearing l2 time, the foot may direct an air blast underneath thepartially lifted sheet to assist inthe separation of the sheet from thepile; v

Surrounding the aforesaid rod ii there is a re.-

action abutment ii for the spring I: and this abutment is connected by alink it to a lever I! which has a follower ll cooperating with theaforesaid cam 9. The shape of the cam is such that after the foot hasbeen lowered 'on to the pile there is a clearance between the cam andthe follower on the bell crank lever. Further rotation of the cam bringsit into engagement with the follower IS on the lever I! connected to theabutment l5 and rotates this lever in a direction to move the abutmentalong the rod to compress the spring thereby increasing the pressureexerted by the foot on the pile. Still further rotation of the camreleases the increased pressure and then brings the cam intore-engagement with the follower 8 on the bell crank lever to lift thefoot off the pile and thereby to free the Pile from the pressure of thefoot and'to allow sheets which may have been lifted or disturbed by theremoval of the top sheet to fall back to their initial position.

In the second example (illustrated in Figure 2),

which is connected by a tension spring 24 to the bell crank lever 1 andthe arrangement is such that after the foot has been lowered on to thepile by the compression spring I: surrounding the guide rod II, the cam2| operates to increase the tension in the tension spring 24 and therebyto increase the pressure of the foot on the pile.

A more specific description of the complete method of separationaccording to the invention is as follows.

In this method nozzles 25 situated at the rear of the pile first directblasts of air into the topmost portion of the pile, thus agitating thesheets and partially separating them. The sheets are prevented frommoving in any direction other than a vertical one, by suitable guidesplaced around the four sides or corners of the pile. When suiiicient airhas entered between the sheets the hollow presser feet 4 descend andrest on the top of the pile with an initial limited pres-.

sure as described in the above example. This pressure is so limited thatit is not so heavy as to press out all the air from between the sheetsor to prevent the top sheet from being drawn or snatched out from underthe presser feet.

After the presser feet have reached the top of the pile, the suctioncups descend and grip the top sheet adjacent to the stops. The suckersare then caused to lift quickly, thus buckling and drawing out the topsheet from beneath the presser feet.

The presser feet are then given the secondary and heavier pressure so asto clamp down the remaining' sheets in the pile. A blast of air is thendirected through the presser feet between the partially lifted sheet andthe pile, thus completely separating the sheet.

The lifting suckers, which now hold the sheet by its rear edge, may egiven a forward motion so that the sheet moves under the action of theair blast substantially parallel to the top of the pile, so as to feedthe sheet into nipping rollers,

v not shown, situated on the conveying portion of the feeder.Alternatively, the sheet may be transferred from the lifting suckers toa set of forwarding suckers, and thereafter pushed'forward by air blastwhile controlled by these suckers into the nipping rollers aforesaid.

The air blast from the presser feet remains on during the time that theseparated sheet is being forwarded by the forwarding or lifting suckersto the nipping rollers, after which both suction and air blast are cuton at approximately the same time.

When the sheet has been taken by the forwarding means and the suctionand air blast cut off the presser feet are lifted approximatelyvertically from the pile, air is discharged through the finding nozzles25 and the cycle of operation continued for the next uppermost sheet onthe pile, the lifting and forwarding suckers being returned $3 itheirrearward position in time to per orm e unction of ickin warding thesheets. p g up and for Having thus described my invention, I claim:

1. The method of separating and forwarding sheets one after another fromthe top of a supply thereof, which comprises applying light pressure onthe top of the supply at a predetermined point along an edge thereof,gripping the uppermost sheet of the supply by suction adjacent saidpoint and lifting the gripped sheet to separate it from the supply whilesaid light pressure is applied, forwarding the lifted sheet from thesupply, and increasing said pressure on the supply pile preparatory toto clamp the next or underlying sheet to said supply during relativeforward movement of said lifted sheet.

2. The method edge thereof, gripping the uppermost sheet of the supplyby suction adjacent said spaced points and lifting the gripped sheet toseparate it from the supply while said lightpressure is applied,advancing the lifted sheet relative to the supply, and increasing saidpressure at said points on the supply to hold the next or underlyingsheet against movement with the advancing lifted sheet.

3. The method of separating and forwarding sheets from a supply thereof,which includes the steps of gripping the uppermost sheet of the sup- 1ply by suction at a predetermined point along and inwardly of an edgethereof and lifting the gripped sheet to separate the same from thesupply, lightly pressing said uppermost sheet against the supply at saidedge and adjacent said point to cause said sheet to buckle uponseparation thereof from the supply and thereafter increasing thepressure on the supply below the separated uppermost sheet to hold thenext or underlying sheet against movement relative to the supply.

4. The method of separating and forwarding sheets one at a time from thetop of a pile, which comprises exerting light pressure on the top of thepile through a presser foot, causing a sucker to grip the top sheet ofthe pile in advance of said presser foot and pull the sheet out fromunder the presser foot, advancing the top sheet.

of feeding sheets from a supply. thereof, which comprises applying lightpressure on the top of the supply atspaced points along an increasingthe pressure exerted by said presserfoot to hold down the remainingsheets of the pile while said top sheet is advanced, lifting the presserfoot and flufiing the sheets at the top of the repeating the cycle.

5. In apparatus for feeding sheets one after another from a supplythereof, means yieldably holding an edge portion of the topmost sheet inengagement with the supply, suction means operable toward and away fromthe supply to grip the topmost sheet adjacent the holding means and drawsaid sheet from beneath said holding I means to separate the same fromsaid supply, and means operable after said topmost sheet is separatedfrom said supply to apply increased pressure on said holding means tohold the remaining sheets of the supply against movement.

6. In apparatus of the class described, suction means operable toelevate a marginal portion of a sheet to separate the same from the topof a "supply of sheets, spring actuated means engaged with the top ofsaid supply for yieldingly resisting upward movement of the top sheetfrom said supply by said suction means and means for increasing thedownward pressure exerted by said spring actuated means for firmlyholding the remaining sheets of said supply against movement after saidtop sheet has been separated from the supply by said suction means.

'7. In a sheet feeder, a presser foot movable into engagement with thetop of a supply of sheets across a margin thereof, means for moving saidpresser foot into engagement with said 7 supply and for applying lightpressure thereon,

and means for thereafter increasing the downward pressure exerted bysaid presser foot.

8. In a sheet feeder, a presser foot movable into engagement with thetop of a will!!! of for controlling the operations of said last namedmeans.

9. In a sheet feeder, a device engaged with the top of a supply ofsheets under limited downward pressure to enable separation of the topsheet from said supply, and operable to apply increased downwardpressure on said supply for preventing forward movement of a succeedingsheet or sheets with a preceding sheet separated from said supply, meansacting to apply said limited downward pressure upon said device, andmeans acting thereafter to apply said increased downward pressure uponsaid device.

10. In apparatus for feedingsheets from the top of a pile, a presserfoot adapted to engage the uppermost sheet of the pile at the rearthereof, a spring means effective to exert light pressure upon saidpresser foot during part of the feeding cycle and means for modifyingthe action of said spring means for exerting increased pressure uponsaid presser foot during another part of the cycle, whereby a sheet maybe pulled out from under the presser foot while the latter is underlight pressure and the remaining sheets of the pile may be firmly heldby the presser foot while under increased pressure.

7 11. Apparatus as defined in claim 10, comprising a spring for urgingsaid presser foot into engagement with the pile and means for increasingthe force exerted by said spring after the presser foot has engaged thepile.

12. Apparatus as defined in claim ll, wherein said means for increasingthe force of the spring comprises a reaction abutment for the spring andmeans for moving said abutment to increase'the loading of the springafter engagement of the presser foot with the pile. I

13. Apparatus as defined in claim 12, comprising a rotating cam adaptedto oppose the action of said spring and functioning to permit the springto lower said presser foot into enga ement with the pile, and comprisingmeans responsive to the same cam for moving said reaction abutment asaforesaid after the presser foot has been lowered.

14. Apparatus as defined in claim 8, comprising a spring for loweringsaid presser foot onto the pile and applying initial pressure to thepile, a rotating cam for controlling the lowering action, a secondspring adapted to exert downward pressure. on said presser foot, andmeans functioning after said presser foot with the pile for loading saidsecond spring.

15. Apparatus as defined in claim 14, wherein the means forloading saidsecond spring comprises a secondcam rotating in synchronism with saidfirst cam.

HEADLEY TOWNSEND BACKHOUSE.

I REFERENCES CITED The following references are of record in the -fileof this patent:

. UNITED STATES PATENTS Number is in engagement

